1. Field of the Invention
This invention relates to abuse resistant, impact resistant and fire resistant building materials, and more particularly, to a single piece laminate composite building material of fiber-cement and gypsum.
2. Description of the Related Art
The interior wallboard market has been dominated by the use of gypsum wallboard products for many years. The gypsum wallboard typically comprises thin paper layers wrapped around a gypsum core. For example, one paper layer covers the face and long edges of the board, and the second paper layer usually covers the back surface of the board. The core is predominantly gypsum, and can be modified with additives such as glass fiber, vermiculite and mica to improve fire resistance.
In addition to fire resistance, abuse resistance is another desired quality in wallboards. Gypsum has poor abuse resistance compared to other wallboard materials such as wood or masonry. The paper surface of gypsum wallboard is easily damaged by impact such as scuffing, indentation, cracking or penetration with hard or soft body objects such as furniture, trolleys, toys, sports equipment and other industrial or residential furnishings. Such wall abuse is typical in high traffic rooms such as corridors, family living areas, gymnasiums or change rooms.
Gypsum wallboard manufacturers have made modifications to their gypsum wallboards to improve their abuse resistance. One method was to bond a plastic film to the back of the wall panel to resist penetration of the impact bodies into the framed wall cavity. Another method was to make a fiber-gypsum wall panel with fiber-gypsum outer layers formed onto a gypsum-based core. These products typically have improved surface abuse resistance to the paper surface of normal gypsum wallboard. Similar gypsum-based or cement gypsum-based compositions are typically described in U.S. Pat. Nos. 5,817,262 and 5,718,759.
One material having significant abuse resistance is fiber-cement. Fiber cement has an advantage over gypsum panel with respect to surface abuse resistance such as wear and abrasion. One disadvantage of fiber cement by itself as a wall panel is that it does not have a fire resistance rating comparable to gypsum wall panels of equal thickness. Another disadvantage of fiber cement by itself is that it is significantly heavier than gypsum wall panels of equivalent thickness. For example, a 1 hour fire resistance-rated wall system with fiber cement requires mineral insulation in the wall cavity or a sub-layer of fire rated gypsum wall panel to achieve a 1 hour fire resistance rating when tested in accordance with ASTM E-119.
A 2-layer system of xc2xcxe2x80x3 fiber cement over ⅝xe2x80x3 type X fire rated gypsum wallboard has been used to achieve both fire resistance and abuse resistance. Such a system is described in Gypsum Associationxe2x80x94Fire Resistance Design Manualxe2x80x94GA FILE NO. WP 1295xe2x80x94Gypsum wallboard, steel studs, fiber-cement board proprietary system. This two piece system is disadvantageous because it is significantly heavier than single-layer gypsum wallboards. Additionally, the 2-layer wallboards require nearly double the amount of labor for installation because two separate wall panels must be installed instead of a single panel. Also, the extra thickness of the 2-layer systems (⅝xe2x80x3+xc2xcxe2x80x3=xe2x85x9exe2x80x3) is not compatible with most doorjamb widths.
Accordingly, what is needed is a single piece building material that has good abuse resistance, impact resistance and fire resistance. This building material should also be light, easy to manufacture and compatible with standard building material sizes. With respect to fire resistance, it would be especially advantageous for such a material to have a fire resistance rating of at least one hour as measured by ASTM E119.
Briefly stated, the needs addressed above are satisfied in one embodiment by a building material comprising fiber-cement laminated to gypsum to form a single piece laminate composite. This single piece laminate composite exhibits improved fire resistance and surface abuse resistance, but achieves these properties without the excessive weight and thickness of two piece systems. Additionally, because of the reduced thickness, the preferred laminate building material is easier to cut and is quicker and easier to install than two piece systems. Furthermore, forming the fiber-cement and gypsum into a single piece laminate eliminates the need to install two separate pieces of building material, thereby simplifying installation.
One object of the invention is to provide a building board product suitable for applications requiring surface abuse resistance, improved impact resistance and a 1-hour fire resistance rating (as measured, for example, by ASTM E-119) without cavity insulation at a panel thickness of ⅝xe2x80x3, installed on each side of a wall frame. The surface abuse resistance is measured by abrasion tests such as ASTM D4977-98b (Standard Test Method for Granule Adhesion to Mineral Surfaced Roofing) and also indentation tests such as ASTM D5420 (Impact Resistance of Flat, Rigid Plastic Specimen by Means of a Striker by a Falling Weight (Gardner Impact)). The panel impact resistance is typically measured by, for example, ASTM E695 (Measuring Relative Resistance of Wall, Floor and Roof Construction to Impact Loading), and ISO 7892 (Vertical Building Elementsxe2x80x94Impact Resistance Testsxe2x80x94Impact Bodies and General Test Procedures), or other suitable impact or abrasion tests.